Lockbox 3 - Difference in Delphi XE5 and Delphi 11.1

I have an old application written in Delphi XE5 using Lockbox 3. I'm upgrading the application to Delphi 11.1. Using the same Lockbox 3 source in Delphi 11.1, when sending the same string (in 11.1 and XE5) into DecryptSymStr, I get totally different results from Delphi XE5. Any ideas on what could cause this?